/*
 * @(#)HashMap.java    Aug 7, 2010
 *
 * Copyright 2009 Nyber(Shanghai Itd. All rights reserved.
 */

package com.lab.util.collection;

/**
 * Class description goes here.
 *
 * @author nickevin@gmail.com
 * @version Aug 7, 2010 2:14:54 PM
 */

/*
 * @(#)HashMap.java	1.68 06/06/27
 *
 * Copyright 2006 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

import java.io.IOException;
import java.io.Serializable;
import java.util.AbstractCollection;
import java.util.AbstractSet;
import java.util.Collection;
import java.util.ConcurrentModificationException;
import java.util.Iterator;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.Set;

public class HashMap<K, V> extends AbstractMap<K, V> implements Map<K, V>,
		Cloneable, Serializable {

	static final int DEFAULT_INITIAL_CAPACITY = 16;
	static final int MAXIMUM_CAPACITY = 1 << 30;
	static final float DEFAULT_LOAD_FACTOR = 0.75f;
	transient Entry[] table;
	transient int size;
	int threshold;
	final float loadFactor;
	transient volatile int modCount;

	public HashMap(int initialCapacity, float loadFactor) {
		if (initialCapacity < 0) {
			throw new IllegalArgumentException("Illegal initial capacity: "
					+ initialCapacity);
		}
		if (initialCapacity > MAXIMUM_CAPACITY) {
			initialCapacity = MAXIMUM_CAPACITY;
		}
		if (loadFactor <= 0 || Float.isNaN(loadFactor)) {
			throw new IllegalArgumentException("Illegal load factor: "
					+ loadFactor);
		}

		int capacity = powerOf2(initialCapacity);
		this.loadFactor = loadFactor;
		threshold = (int) (capacity * loadFactor);
		table = new Entry[capacity];
		init();
	}

	// Find a power of 2 >= initialCapacity
	private int powerOf2(int initialCapacity) {
		int capacity = 1;
		while (capacity < initialCapacity) {
			capacity <<= 1;
		}
		return capacity;
	}

	public HashMap(int initialCapacity) {
		this(initialCapacity, DEFAULT_LOAD_FACTOR);
	}

	public HashMap() {
		this.loadFactor = DEFAULT_LOAD_FACTOR;
		threshold = (int) (DEFAULT_INITIAL_CAPACITY * DEFAULT_LOAD_FACTOR);
		table = new Entry[DEFAULT_INITIAL_CAPACITY];
		init();
	}

	public HashMap(Map<? extends K, ? extends V> m) {
		this(Math.max((int) (m.size() / DEFAULT_LOAD_FACTOR) + 1,
				DEFAULT_INITIAL_CAPACITY), DEFAULT_LOAD_FACTOR);
		putAllForCreate(m);
	}

	// internal utilities

	/**
	 * Initialization hook for subclasses. This method is called
	 * in all constructors and pseudo-constructors (clone, readObject)
	 * after HashMap has been initialized but before any entries have
	 * been inserted.  (In the absence of this method, readObject would
	 * require explicit knowledge of subclasses.)
	 */
	void init() {}

	static final Object NULL_KEY = new Object();

	static <T> T maskNull(T key) {
		return key == null ? (T) NULL_KEY : key;
	}

	static <T> T unmaskNull(T key) {
		return key == NULL_KEY ? null : key;
	}

	/**
	 * Whether to prefer the old supplemental hash function, for
	 * compatibility with broken applications that rely on the
	 * internal hashing order.
	 *
	 * Set to true only by hotspot when invoked via
	 * -XX:+UseNewHashFunction or -XX:+AggressiveOpts
	 */
	private static final boolean useNewHash;
	static {
		useNewHash = false;
	}

	private static int oldHash(int h) {
		h += ~(h << 9);
		h ^= h >>> 14;
		h += h << 4;
		h ^= h >>> 10;
		return h;
	}

	private static int newHash(int h) {
		// This function ensures that hashCodes that differ only by
		// constant multiples at each bit position have a bounded
		// number of collisions (approximately 8 at default load factor).
		h ^= h >>> 20 ^ h >>> 12;
		return h ^ h >>> 7 ^ h >>> 4;
	}

	/**
	 * Applies a supplemental hash function to a given hashCode, which
	 * defends against poor quality hash functions.  This is critical
	 * because HashMap uses power-of-two length hash tables, that
	 * otherwise encounter collisions for hashCodes that do not differ
	 * in lower bits.
	 */
	static int hash(int h) {
		return useNewHash ? newHash(h) : oldHash(h);
	}

	static int hash(Object key) {
		return hash(key.hashCode());
	}

	/** 
	 * Check for equality of non-null reference x and possibly-null y. 
	 */
	static boolean eq(Object x, Object y) {
		return x == y || x.equals(y);
	}

	/**
	 * Returns index for hash code h. 
	 * 
	 * length为2的幂次方, 则length- 1的二进制都为1, 目的有二: 
	 * 		1. 保证计算得到的索引值总是位于 table 数组的索引之内.
	 * 		2. 由于二进制都为1, 所以可以更好地设计hash code以减少碰撞次数.
	 * 
	 */
	static int indexFor(int hash, int length) {
		return hash & length - 1; // 使用高效的与操作代替低效的取模. 
	}

	@Override
	public int size() {
		return size;
	}

	@Override
	public boolean isEmpty() {
		return size == 0;
	}

	@Override
	public V get(Object key) {
		if (key == null) {
			return getForNullKey();
		}

		int hash = hash(key.hashCode());
		int i = indexFor(hash, table.length);
		for (Entry<K, V> e = table[i]; e != null; e = e.next) {
			Object k;
			if (e.hash == hash && ((k = e.key) == key || key.equals(k))) {
				return e.value;
			}
		}

		return null;
	}

	private V getForNullKey() {
		int hash = hash(NULL_KEY.hashCode());
		int i = indexFor(hash, table.length);
		Entry<K, V> e = table[i];
		while (true) {
			if (e == null) {
				return null;
			}
			if (e.key == NULL_KEY) {
				return e.value;
			}
			e = e.next;
		}
	}

	@Override
	public boolean containsKey(Object key) {
		Object k = maskNull(key);
		int hash = hash(k.hashCode());
		int i = indexFor(hash, table.length);
		Entry e = table[i];
		while (e != null) {
			if (e.hash == hash && eq(k, e.key)) {
				return true;
			}
			e = e.next;
		}
		return false;
	}

	/**
	 * Returns the entry associated with the specified key in the
	 * HashMap.  Returns null if the HashMap contains no mapping
	 * for this key.
	 */
	Entry<K, V> getEntry(Object key) {
		Object k = maskNull(key);
		int hash = hash(k.hashCode());
		int i = indexFor(hash, table.length);
		Entry<K, V> e = table[i];
		while (e != null && !(e.hash == hash && eq(k, e.key))) {
			e = e.next;
		}
		return e;
	}

	/** 
	 * hashCode不同也可能位于同一个索引.
	 * 
	 */
	@Override
	public V put(K key, V value) {
		if (key == null) {
			return putForNullKey(value);
		}

		int hash = hash(key.hashCode());
		int bucketIndex = indexFor(hash, table.length);
		// System.out.println(key + " " + value + " " + hash + " " + bucketIndex);

		if (isDuplicatedKey(key, value, hash, bucketIndex)) {
			return oldValue;
		}

		modCount++;
		addEntry(hash, key, value, bucketIndex);

		return null;
	}

	V oldValue;

	private boolean isDuplicatedKey(K key, V value, int hash, int i) {
		for (Entry<K, V> e = table[i]; e != null; e = e.next) {
			Object k;
			if (e.hash == hash && ((k = e.key) == key || key.equals(k))) {
				oldValue = e.value;
				e.value = value;
				e.recordAccess(this);

				return true;
			}
		}

		return false;
	}

	private V putForNullKey(V value) {
		int hash = hash(NULL_KEY.hashCode());
		int i = indexFor(hash, table.length);

		for (Entry<K, V> e = table[i]; e != null; e = e.next) {
			if (e.key == NULL_KEY) {
				V oldValue = e.value;
				e.value = value;
				e.recordAccess(this);
				return oldValue;
			}
		}

		modCount++;
		addEntry(hash, (K) NULL_KEY, value, i);
		return null;
	}

	/**
	 * This method is used instead of put by constructors and
	 * pseudoconstructors (clone, readObject).  It does not resize the table,
	 * check for comodification, etc.  It calls createEntry rather than
	 * addEntry.
	 */
	private void putForCreate(K key, V value) {
		K k = maskNull(key);
		int hash = hash(k.hashCode());
		int i = indexFor(hash, table.length);

		/**
		 * Look for preexisting entry for key.  This will never happen for
		 * clone or deserialize.  It will only happen for construction if the
		 * input Map is a sorted map whose ordering is inconsistent w/ equals.
		 */
		for (Entry<K, V> e = table[i]; e != null; e = e.next) {
			if (e.hash == hash && eq(k, e.key)) {
				e.value = value;
				return;
			}
		}

		createEntry(hash, k, value, i);
	}

	void putAllForCreate(Map<? extends K, ? extends V> m) {
		for (Iterator<? extends Map.Entry<? extends K, ? extends V>> i = m
				.entrySet().iterator(); i.hasNext();) {
			Map.Entry<? extends K, ? extends V> e = i.next();
			putForCreate(e.getKey(), e.getValue());
		}
	}

	/**
	 * Copies all of the mappings from the specified map to this map
	 * These mappings will replace any mappings that
	 * this map had for any of the keys currently in the specified map.
	 *
	 * @param m mappings to be stored in this map.
	 * @throws NullPointerException if the specified map is null.
	 */
	@Override
	public void putAll(Map<? extends K, ? extends V> m) {
		int numKeysToBeAdded = m.size();
		if (numKeysToBeAdded == 0) {
			return;
		}

		/*
		 * Expand the map if the map if the number of mappings to be added
		 * is greater than or equal to threshold.  This is conservative; the
		 * obvious condition is (m.size() + size) >= threshold, but this
		 * condition could result in a map with twice the appropriate capacity,
		 * if the keys to be added overlap with the keys already in this map.
		 * By using the conservative calculation, we subject ourself
		 * to at most one extra resize.
		 */
		if (numKeysToBeAdded > threshold) {
			int targetCapacity = (int) (numKeysToBeAdded / loadFactor + 1);
			if (targetCapacity > MAXIMUM_CAPACITY) {
				targetCapacity = MAXIMUM_CAPACITY;
			}
			int newCapacity = table.length;
			while (newCapacity < targetCapacity) {
				newCapacity <<= 1;
			}
			if (newCapacity > table.length) {
				resize(newCapacity);
			}
		}

		for (Iterator<? extends Map.Entry<? extends K, ? extends V>> i = m
				.entrySet().iterator(); i.hasNext();) {
			Map.Entry<? extends K, ? extends V> e = i.next();
			put(e.getKey(), e.getValue());
		}
	}

	/**
	 * Removes the mapping for this key from this map if present.
	 *
	 * @param  key key whose mapping is to be removed from the map.
	 * @return previous value associated with specified key, or <tt>null</tt>
	 *	       if there was no mapping for key.  A <tt>null</tt> return can
	 *	       also indicate that the map previously associated <tt>null</tt>
	 *	       with the specified key.
	 */
	@Override
	public V remove(Object key) {
		Entry<K, V> e = removeEntryForKey(key);
		return e == null ? null : e.value;
	}

	/**
	 * Removes and returns the entry associated with the specified key
	 * in the HashMap.  Returns null if the HashMap contains no mapping
	 * for this key.
	 */
	Entry<K, V> removeEntryForKey(Object key) {
		Object k = maskNull(key);
		int hash = hash(k.hashCode());
		int i = indexFor(hash, table.length);
		Entry<K, V> prev = table[i];
		Entry<K, V> e = prev;

		while (e != null) {
			Entry<K, V> next = e.next;
			if (e.hash == hash && eq(k, e.key)) {
				modCount++;
				size--;
				if (prev == e) {
					table[i] = next;
				} else {
					prev.next = next;
				}
				e.recordRemoval(this);
				return e;
			}
			prev = e;
			e = next;
		}

		return e;
	}

	/**
	 * Special version of remove for EntrySet.
	 */
	Entry<K, V> removeMapping(Object o) {
		if (!(o instanceof Map.Entry)) {
			return null;
		}

		Map.Entry<K, V> entry = (Map.Entry<K, V>) o;
		Object k = maskNull(entry.getKey());
		int hash = hash(k.hashCode());
		int i = indexFor(hash, table.length);
		Entry<K, V> prev = table[i];
		Entry<K, V> e = prev;

		while (e != null) {
			Entry<K, V> next = e.next;
			if (e.hash == hash && e.equals(entry)) {
				modCount++;
				size--;
				if (prev == e) {
					table[i] = next;
				} else {
					prev.next = next;
				}
				e.recordRemoval(this);
				return e;
			}
			prev = e;
			e = next;
		}

		return e;
	}

	/**
	 * Removes all mappings from this map.
	 */
	@Override
	public void clear() {
		modCount++;
		Entry[] tab = table;
		for (int i = 0; i < tab.length; i++) {
			tab[i] = null;
		}
		size = 0;
	}

	/**
	 * Returns <tt>true</tt> if this map maps one or more keys to the
	 * specified value.
	 *
	 * @param value value whose presence in this map is to be tested.
	 * @return <tt>true</tt> if this map maps one or more keys to the
	 *         specified value.
	 */
	@Override
	public boolean containsValue(Object value) {
		if (value == null) {
			return containsNullValue();
		}

		Entry[] tab = table;
		for (int i = 0; i < tab.length; i++) {
			for (Entry e = tab[i]; e != null; e = e.next) {
				if (value.equals(e.value)) {
					return true;
				}
			}
		}
		return false;
	}

	/**
	 * Special-case code for containsValue with null argument
	 **/
	private boolean containsNullValue() {
		Entry[] tab = table;
		for (int i = 0; i < tab.length; i++) {
			for (Entry e = tab[i]; e != null; e = e.next) {
				if (e.value == null) {
					return true;
				}
			}
		}
		return false;
	}

	/**
	 * Returns a shallow copy of this <tt>HashMap</tt> instance: the keys and
	 * values themselves are not cloned.
	 *
	 * @return a shallow copy of this map.
	 */
	@Override
	public Object clone() {
		HashMap<K, V> result = null;
		try {
			result = (HashMap<K, V>) super.clone();
		} catch (CloneNotSupportedException e) {
			// assert false;
		}
		result.table = new Entry[table.length];
		result.entrySet = null;
		result.modCount = 0;
		result.size = 0;
		result.init();
		result.putAllForCreate(this);

		return result;
	}

	static class Entry<K, V> implements Map.Entry<K, V> {
		final K key;
		V value;
		final int hash;
		Entry<K, V> next;

		/**
		 * Create new entry.
		 */
		Entry(int h, K k, V v, Entry<K, V> n) {
			value = v;
			next = n;
			key = k;
			hash = h;
		}

		public K getKey() {
			return HashMap.<K> unmaskNull(key);
		}

		public V getValue() {
			return value;
		}

		public V setValue(V newValue) {
			V oldValue = value;
			value = newValue;
			return oldValue;
		}

		@Override
		public boolean equals(Object o) {
			if (!(o instanceof Map.Entry)) {
				return false;
			}
			Map.Entry e = (Map.Entry) o;
			Object k1 = getKey();
			Object k2 = e.getKey();
			if (k1 == k2 || k1 != null && k1.equals(k2)) {
				Object v1 = getValue();
				Object v2 = e.getValue();
				if (v1 == v2 || v1 != null && v1.equals(v2)) {
					return true;
				}
			}
			return false;
		}

		@Override
		public int hashCode() {
			return (key == NULL_KEY ? 0 : key.hashCode())
					^ (value == null ? 0 : value.hashCode());
		}

		@Override
		public String toString() {
			return getKey() + "=" + getValue();
		}

		/**
		 * This method is invoked whenever the value in an entry is
		 * overwritten by an invocation of put(k,v) for a key k that's already
		 * in the HashMap.
		 */
		void recordAccess(HashMap<K, V> m) {}

		/**
		 * This method is invoked whenever the entry is
		 * removed from the table.
		 */
		void recordRemoval(HashMap<K, V> m) {}
	}

	void addEntry(int hash, K key, V value, int bucketIndex) {
		Entry<K, V> e = table[bucketIndex];
		table[bucketIndex] = new Entry<K, V>(hash, key, value, e);
		if (isMoreThanThreshold()) {
			resize(2 * table.length);
		}
	}

	void resize(int newCapacity) {
		Entry[] oldTable = table;
		int oldCapacity = oldTable.length;
		if (oldCapacity == MAXIMUM_CAPACITY) {
			threshold = Integer.MAX_VALUE;

			return;
		}

		Entry[] newTable = new Entry[newCapacity];
		rebuild(newTable);
		table = newTable;
		threshold = (int) (newCapacity * loadFactor);
	}

	void rebuild(Entry[] newTable) {
		Entry[] src = table;
		int newCapacity = newTable.length;
		for (int j = 0; j < src.length; j++) {
			Entry<K, V> e = src[j];
			if (e != null) {
				src[j] = null;
				do {
					Entry<K, V> next = e.next;
					int i = indexFor(e.hash, newCapacity);
					e.next = newTable[i];
					newTable[i] = e;
					e = next;
				} while (e != null);
			}
		}
	}

	private boolean isMoreThanThreshold() {
		return size++ >= threshold;
	}

	/**
	 * Like addEntry except that this version is used when creating entries
	 * as part of Map construction or "pseudo-construction" (cloning,
	 * deserialization).  This version needn't worry about resizing the table.
	 *
	 * Subclass overrides this to alter the behavior of HashMap(Map),
	 * clone, and readObject.
	 */
	void createEntry(int hash, K key, V value, int bucketIndex) {
		Entry<K, V> e = table[bucketIndex];
		table[bucketIndex] = new Entry<K, V>(hash, key, value, e);
		size++;
	}

	private abstract class HashIterator<E> implements Iterator<E> {
		Entry<K, V> next; // next entry to return
		int expectedModCount; // For fast-fail 
		int index; // current slot 
		Entry<K, V> current; // current entry

		HashIterator() {
			expectedModCount = modCount;
			Entry[] t = table;
			int i = t.length;
			Entry<K, V> n = null;
			if (size != 0) { // advance to first entry
				while (i > 0 && (n = t[--i]) == null) {
					;
				}
			}
			next = n;
			index = i;
		}

		public boolean hasNext() {
			return next != null;
		}

		Entry<K, V> nextEntry() {
			if (modCount != expectedModCount) {
				throw new ConcurrentModificationException();
			}
			Entry<K, V> e = next;
			if (e == null) {
				throw new NoSuchElementException();
			}

			Entry<K, V> n = e.next;
			Entry[] t = table;
			int i = index;
			while (n == null && i > 0) {
				n = t[--i];
			}
			index = i;
			next = n;
			return current = e;
		}

		public void remove() {
			if (current == null) {
				throw new IllegalStateException();
			}
			if (modCount != expectedModCount) {
				throw new ConcurrentModificationException();
			}
			Object k = current.key;
			current = null;
			HashMap.this.removeEntryForKey(k);
			expectedModCount = modCount;
		}

	}

	private class ValueIterator extends HashIterator<V> {
		public V next() {
			return nextEntry().value;
		}
	}

	private class KeyIterator extends HashIterator<K> {
		public K next() {
			return nextEntry().getKey();
		}
	}

	private class EntryIterator extends HashIterator<Map.Entry<K, V>> {
		public Map.Entry<K, V> next() {
			return nextEntry();
		}
	}

	// Subclass overrides these to alter behavior of views' iterator() method
	Iterator<K> newKeyIterator() {
		return new KeyIterator();
	}

	Iterator<V> newValueIterator() {
		return new ValueIterator();
	}

	Iterator<Map.Entry<K, V>> newEntryIterator() {
		return new EntryIterator();
	}

	// Views

	private transient Set<Map.Entry<K, V>> entrySet = null;

	/**
	 * Returns a set view of the keys contained in this map.  The set is
	 * backed by the map, so changes to the map are reflected in the set, and
	 * vice-versa.  The set supports element removal, which removes the
	 * corresponding mapping from this map, via the <tt>Iterator.remove</tt>,
	 * <tt>Set.remove</tt>, <tt>removeAll</tt>, <tt>retainAll</tt>, and
	 * <tt>clear</tt> operations.  It does not support the <tt>add</tt> or
	 * <tt>addAll</tt> operations.
	 *
	 * @return a set view of the keys contained in this map.
	 */
	@Override
	public Set<K> keySet() {
		Set<K> ks = keySet;
		return ks != null ? ks : (keySet = new KeySet());
	}

	private class KeySet extends AbstractSet<K> {
		@Override
		public Iterator<K> iterator() {
			return newKeyIterator();
		}

		@Override
		public int size() {
			return size;
		}

		@Override
		public boolean contains(Object o) {
			return containsKey(o);
		}

		@Override
		public boolean remove(Object o) {
			return HashMap.this.removeEntryForKey(o) != null;
		}

		@Override
		public void clear() {
			HashMap.this.clear();
		}
	}

	/**
	 * Returns a collection view of the values contained in this map.  The
	 * collection is backed by the map, so changes to the map are reflected in
	 * the collection, and vice-versa.  The collection supports element
	 * removal, which removes the corresponding mapping from this map, via the
	 * <tt>Iterator.remove</tt>, <tt>Collection.remove</tt>,
	 * <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt> operations.
	 * It does not support the <tt>add</tt> or <tt>addAll</tt> operations.
	 *
	 * @return a collection view of the values contained in this map.
	 */
	@Override
	public Collection<V> values() {
		Collection<V> vs = values;
		return vs != null ? vs : (values = new Values());
	}

	private class Values extends AbstractCollection<V> {
		@Override
		public Iterator<V> iterator() {
			return newValueIterator();
		}

		@Override
		public int size() {
			return size;
		}

		@Override
		public boolean contains(Object o) {
			return containsValue(o);
		}

		@Override
		public void clear() {
			HashMap.this.clear();
		}
	}

	/**
	 * Returns a collection view of the mappings contained in this map.  Each
	 * element in the returned collection is a <tt>Map.Entry</tt>.  The
	 * collection is backed by the map, so changes to the map are reflected in
	 * the collection, and vice-versa.  The collection supports element
	 * removal, which removes the corresponding mapping from the map, via the
	 * <tt>Iterator.remove</tt>, <tt>Collection.remove</tt>,
	 * <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt> operations.
	 * It does not support the <tt>add</tt> or <tt>addAll</tt> operations.
	 *
	 * @return a collection view of the mappings contained in this map.
	 * @see Map.Entry
	 */
	@Override
	public Set<Map.Entry<K, V>> entrySet() {
		Set<Map.Entry<K, V>> es = entrySet;
		return es != null ? es : (entrySet = new EntrySet());
	}

	private class EntrySet extends AbstractSet/*<Map.Entry<K,V>>*/{
		@Override
		public Iterator/*<Map.Entry<K,V>>*/iterator() {
			return newEntryIterator();
		}

		@Override
		public boolean contains(Object o) {
			if (!(o instanceof Map.Entry)) {
				return false;
			}
			Map.Entry<K, V> e = (Map.Entry<K, V>) o;
			Entry<K, V> candidate = getEntry(e.getKey());
			return candidate != null && candidate.equals(e);
		}

		@Override
		public boolean remove(Object o) {
			return removeMapping(o) != null;
		}

		@Override
		public int size() {
			return size;
		}

		@Override
		public void clear() {
			HashMap.this.clear();
		}
	}

	/**
	 * Save the state of the <tt>HashMap</tt> instance to a stream (i.e.,
	 * serialize it).
	 *
	 * @serialData The <i>capacity</i> of the HashMap (the length of the
	 *		   bucket array) is emitted (int), followed  by the
	 *		   <i>size</i> of the HashMap (the number of key-value
	 *		   mappings), followed by the key (Object) and value (Object)
	 *		   for each key-value mapping represented by the HashMap
	 *             The key-value mappings are emitted in the order that they
	 *             are returned by <tt>entrySet().iterator()</tt>.
	 * 
	 */
	private void writeObject(java.io.ObjectOutputStream s) throws IOException {
		Iterator<Map.Entry<K, V>> i = entrySet().iterator();

		// Write out the threshold, loadfactor, and any hidden stuff
		s.defaultWriteObject();

		// Write out number of buckets
		s.writeInt(table.length);

		// Write out size (number of Mappings)
		s.writeInt(size);

		// Write out keys and values (alternating)
		while (i.hasNext()) {
			Map.Entry<K, V> e = i.next();
			s.writeObject(e.getKey());
			s.writeObject(e.getValue());
		}
	}

	private static final long serialVersionUID = 362498820763181265L;

	/**
	 * Reconstitute the <tt>HashMap</tt> instance from a stream (i.e.,
	 * deserialize it).
	 */
	private void readObject(java.io.ObjectInputStream s) throws IOException,
			ClassNotFoundException {
		// Read in the threshold, loadfactor, and any hidden stuff
		s.defaultReadObject();

		// Read in number of buckets and allocate the bucket array;
		int numBuckets = s.readInt();
		table = new Entry[numBuckets];

		init(); // Give subclass a chance to do its thing.

		// Read in size (number of Mappings)
		int size = s.readInt();

		// Read the keys and values, and put the mappings in the HashMap
		for (int i = 0; i < size; i++) {
			K key = (K) s.readObject();
			V value = (V) s.readObject();
			putForCreate(key, value);
		}
	}

	// These methods are used when serializing HashSets
	int capacity() {
		return table.length;
	}

	float loadFactor() {
		return loadFactor;
	}
}
